This relates generally to imaging systems and, more particularly, to photon counting complementary metal-oxide-semiconductor (CMOS) image sensor arrays with pixels that use single-photon avalanche diodes (SPADs) for single photon detection and that are illuminated from the back side of the substrate.
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Image sensors (sometimes referred to as imagers) may be formed from a two-dimensional array of image sensing pixels. Each pixel includes a photosensitive element that receives incident photons (light) and converts the photons into electrical signals. Image sensors are sometimes designed to provide images to electronic devices using a Joint Photographic Experts Group (JPEG) format.
Conventional image sensors with back side illuminated pixels may suffer from limited functionality in a variety of ways. For example, some conventional image sensors may not be able to determine the distance from the image sensor to the objects that are being imaged. Conventional image sensors may also have lower than desired image quality and resolution.
It would therefore be desirable to be able to provide improved image sensors with back side illuminated pixels.